Abstract

Background

Non-adherence to inhaled combination therapy (ICT) is a major contributor to poor control in difficult asthma1; however identifying non-adherence in this population is challenging. We have shown that suppression of fractional exhaled nitric oxide (FeNO), following directly observed inhaled corticosteroid can identify non-adherence2; it has previously been suggested that a single high FeNO measurement can identify non-adherence in difficult asthma.

Methods

We performed a retrospective analysis of patients attending a difficult asthma clinic between January 2007 and December 2010. Prescription refill data, patient demographics, FeNO and lung function were collated. ICT prescription refill ratio % was calculated as the number of doses refilled/number of doses prescribed over 6 months × 100.1 Non-parametric correlation analysis was performed. Tests for non-adherence defined as ICT prescription refill cut-offs of <80% and <50% were assessed.

While there is a weak relationship between a single point-in-time FeNO measurement and non-adherence to ICT in difficult asthma, this cannot be used as an alternative to our previously described FeNO suppression test.